1. Field of the Invention
This invention relates to cowl fastener systems for small aircraft and particularly to cowl fastener systems utilizing a single countersunk bushing.
2. Description of the Prior Art
Airplane fastener systems in use today use a three-part fastener that has a screw, a spring-loaded screw body and a receptacle can that is attached to the underside of a cowling or other airplane surface. FIGS. 1-7 illustrate this prior art fastening system. FIG. 1 is a perspective view of a lower retainer 100 can for a spring-loaded fastener system as prior art. This can has a lower body 101, a top flange 102 an internal wall 103 that accepts the screw body, and a threaded center hole 104 that accepts the screw.
FIG. 2 is a perspective view of a prior art spring-loaded fastener body 105 that shows a screw 106 installed in it. FIG. 3 is a detail view of a prior art fastener system, partially assembled. Here, the screw body 105 and screw 106 are positioned above the lower retainer can 100. FIG. 4 is a cross-sectional view of the spring-loaded fastener body view, as prior art. Here, the screw body 105 is shown having a spring 107 installed in it. The screw 106 is shown within the spring. FIG. 5 is a cross-sectional view of the prior art assembled fastener system as prior art. In this view, the lower retainer can 100 is shown riveted to a piece of structure 110 using rivets 111 through the top flange 102. The screw body 105 is shown seated in the internal wall 103 of the retainer can 100 with the bottom of the screw 106 engaging the threads in the threaded center hole 104.
In this design the spring is used to keep tension on the screw so that the screw body remains seated, yet, when the screw is backed off, the screw body pops up from the structure for easy removal, as shown in FIG. 5, where the screw body is above the structure. FIG. 6 is a top detail view of the prior art cowling fastener installed, as prior art. FIG. 7 is perspective detail view of the prior art cowling fastener installed, as prior art. These figures show the device as fully installed, with the screw and screw body flush with the upper surface of the structure
Although this system works, is has limitation in strength because of how it is made and how it is designed to work.